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OWNER'S MANUAL

Pedestal, bevelhead and reduction gearbox maintenance, torque tube, universal joint and draglink installation, gearbox and pedestal mounting geometry and rudder stops for Lewmar (Whitlock) Mamba mechanical steering systems.

DocumentLewmar Mamba Steering Systems Installation & Maintenance Instructions
FormatPDF · 12 pages · 0.6 MB
LanguageEnglish
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PedestalsBevelheads & GearboxesInstallationGeometry TablesPedestal Mounting & StopsProducts
Lewmar Mamba Steering Systems — Installation & Maintenance Instructions

Mamba 3R-DL / 12R-DL

  • Stove-enamelled polyester finish: wash with fresh water and wax with a good car polish. Touch in chips after rubbing down with fine wet-and-dry, using a yacht enamel for aluminium.
  • Socket countersunk deck bolts are recommended; slacken them and reseat in non-setting mastic, holding the screw and turning the nut. Pedestal bolt sets are made in M12 × 90 stainless with heavy duty washer and nut.
  • Once a season: remove the 4 top cover screws, clean and refit with anti-seize cream; inspect the internals.
  • Check bevel mesh: rock the wheel 1 cm (3/8") each way; any backlash is taken out by removing 1 or 2 shims between the input socket assembly and the pedestal bowl (fig. MP1).
  • At each rudder stop, load the wheel and look for movement between shafts and bevel gears – that means worn keys, a job for a service agent.
  • Re-grease the gears; keep water out via the compass cable grommet and top plate gasket. Also remove, clean and refit the 4 stainless input-assembly socket screws with anti-seize (wheel off – do not lose the wheel key).

Mamba 3R / 12R Premiere

  • Aluminium pedestal, stove enamelled, with a GRP head; finish care as above.
  • Fix with stainless cap head screws and the nylon insulating washers supplied; the O-ring in the base groove seals to a smooth level cockpit floor.
  • The head houses a bevel head unit with integral Premiere friction brake (MP2).
  • To reach the bevel head, engine controls or instrument cabling: unscrew the brake spinner, remove the wheel, the 4 button head facia screws and gasket, and the 4 cap head screws between tulip and GRP head, then ease the head off the tulip. Reverse to refit.

Lewmar Mamba Premiere pedestal exploded view MP2

Lewmar Mamba MP1 pedestal exploded view

Bevelhead & Gearbox Maintenance

  • A bevelhead or gearbox fitted directly under the pedestal should be removed and inspected at least once every 3 seasons; smear waterproof grease on the splined or square joint when refitting, and anti-seize on fasteners.
  • Once a season check fastenings and casings (all but the BH08 are stainless and marine grade aluminium). All except the WRG models up to the WRG12 can be adjusted for gear wear.
  • Bevelhead mesh (BH875 / BH100 / BH125, MP3; BH08 / BH10, MP3A): side-load each shaft. Older needle-bearing heads may show up to 2mm at the shaft end; BH08, BH10 and BH150 (deep groove ball bearings) should show none. For backlash, remove one shim at a time from under the output socket until it is gone; do not over-mesh. Hexagon bolts with spring washers, or socket caps with thread locking compound.
  • Gearbox mesh (BG10, BG12, BG30, MP4): with load at the rudder stops, movement of the output shaft or lever means worn bearings or keys – return the gearbox or call a service agent. Remove shims behind the input socket to take up backlash; check oil seals.
  • WRG18, WRG20, WRG45: mesh is set at manufacture by rotating the two eccentric input sockets (MP5A); the eccentric caps must stay in phase – leave adjustment to a service engineer.
  • WRG10, 11, 12, WG08, 16: no mesh adjustment; check bearings and oil seals.

Torque Tubes, Joints & Draglinks

  • Torque tubes come with one end unwelded and over length; the builder cuts and welds (stainless, except the 08 series shaft which is carbon steel – use dissimilar-metal rods such as Sudachrom D or Tec-Arc 312).
  • End fittings adjust on 3/4Ø and 7/8Ø 48 serration splines (08/10 series) or a flatted shaft (125 and 150 series). The shaft must fully engage the universal joint boss; torque the clamping bolts to 30Nm (8mm) or 40Nm (10mm).
  • Universal joints (AMK8 / AMK10, MP8) work up to 25° each; mount them 90° rotated to each other on each tube and equalise the working angles of each pair. (The MP8 drawing labels it "25%", as printed.)
  • Draglinks (AHFT 10 / AHFT 12 / RFQ 16, MP9) are stainless; weld with TEC Weld 312. Keep at least 1 1/2 times the thread diameter engaged in each rose joint, lock with the Nyloc nuts to 40Nm. Rose joints allow up to 20° deflection.
  • Bevel heads must be mounted on a plate or bracket rigid enough not to deflect under full wheel torque, with Nyloc nuts.

Gearbox Mounting

  • The gearbox sees full rudder torque: mount it with no deflection at maximum load, high strength Loctite on bolts with load-spreading and spring washers, Nyloc nuts on studs.
  • Gearbox beside a stock raked up to 20°: set the height so the draglink is near horizontal, then use distance L3 to find offset angle B° (tables below).
  • Stock raked more than 20°: mount the gearbox athwartships at the tiller arm (MP13) and use Fig. 4 for offset X.
  • Vertical gearbox (MP14): the rose joint heights matter – Fig. 5 gives offset Y; the draglink angle at midships should not exceed 5°.
  • WRG11, 12, 18, 20 or 45 mounted directly under the pedestal use an adapter torque plate (MP15/15A): check every season under load at the stops that there is no movement and the bolts are tight – critical.

Gearbox Lever Geometry

Fig. 3(a): output lever 5 1/4"/133mm, tiller lever 8"/253mm (as printed)

Draglink centres L3 B°
200-225 25°
226-250 23°
251-300 20°
301-350 17°
351-400 14°
401-500 12°
501-750 10°
751-1000 8°
1000+ 5°

Fig. 3(b): output lever 7 3/8"/187mm, tiller lever 11 1/4"/286mm

L3 B°2
251-300 25°
301-350 23°
351-400 20°
401-500 15°
501-750 10°
751-1000 8°
1000+ 5°

Fig. 3(c): output lever 13"/332mm, tiller lever 20"/508mm

L3 B°3
350-400 28°
401-500 25°
501-750 20°
751-1000 15°
1000-1500 10°
1501+ 8°

Fig. 4 (MP13) and Fig. 5 (MP14)

X Y R1 output lever centres R2 tiller lever centres
104 ± 5 60 133 203
146 ± 5 84 187 286
260 ± 5 150 332 508

Pedestal Mounting

  • Place it with room and shelter for the helmsman, clear of winches, pumps and locker lids; a guard can stop the mainsheet snagging it in a gybe.
  • Optimum position relative to the seat: Fig. 1.1 (14"/355mm and 8"/203mm shown; standard pedestal centres 28"/710mm, special heights to order).
  • The cockpit sole must not deflect under helm loads: as a guide, GRP at least 40mm total thickness (e.g. 25mm (1") ply sandwiched full width); plywood at least 50mm (2"), e.g. 2 × 18mm ply doublers with 75 × 40mm bearers; steel soles 75 × 60 × 6mm angle stiffening (260mm min. shown).
  • Bolt through with heavy stainless washers or 4 off 75 × 40 × 6 plates; internal-socket countersunk bolts are recommended.

Rudder Stops

  • Rudder stops are essential: on the side of the tiller arm next to the rose joint, rigid enough not to deflect at 150% of the maximum rated rudder torque.
  • Bond a resilient facing to the stop to absorb impact (MP16).
  • Check torque plates, gearbox mounts and stops under load every season.

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